I don't see a market for it. The D3x is rather the specialty product whereas the D3 was something that made photographers of all kinds wet themselves. I doubt a D700x would sell, and if it did the D3x wouldn't

The only reason they might do something like this is to own the shelf. Manufacturers in highly competitive markets will create multiple versions of a nearly identical product so that a buyer at a BigBox retailer walks up to the shelf and sees one manufacturer owning it. Sony perfected this strategy with a number of their products, and are doing the same thing now in the camera segment. Canon and Nikon may follow suit.